Harry F. Harlow (October 31, 1905–1981) was an American psychologist best known for his studies on affection and development using rhesus monkeys and surrogate wire or terrycloth mothers. He earned his BA and Ph.D. from Stanford University, and did his research primarily at the University of Wisconsin.

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Born Harry Israel in Iowa, the third of four sons, he changed his name to Harry Harlow in 1930 at the instigation of one of his teachers concerned with the antisemitism of the era. After a year at Reed College in Portland, Ore. he transferred to Stanford University, where he earned his B.A. and Ph.D.. Hired by the University of Wisconsin-Madison, he established one of the first primate labs in the country and did his research there for over 40 years. His first graduate student was humanistic psychologistAbraham Maslow and the early research was done on primate intelligence. He also established the first domestic breeding colony of primates in the U. S. in 1955. The difficulties in figuring how to raise primate infants led to his famous experiments. (citation D. Blum, Love at Goon Park).

In his most famous experiment, Harlow offered young rhesus monkeys a choice between two surrogate mothers. In the first group, the terrycloth mother provided no food and wire mother provided food. In the second group, the terrycloth mother provided food and the wire mother did not. It was found that the young monkeys spent as little time as possible with the wire mother and otherwise clung to the terrycloth mother whether she could provide them with food or not. Apparently the terrycloth mothers provided something that was more valuable to the young monkeys than food. She was providing contact comfort. Harlow's interpretation - which is still prevalent today - was that the preference for the terrycloth mother demonstrated the importance of affection and emotional nurturance in mother-child relationships.

Whenever a frightening stimulus was brought into the cage the monkeys ran to the cloth mother for protection and comfort no matter which mother provided them with food. Surprisingly, this response only increased as the monkeys grew older.

Also, when the monkeys were placed in a strange, new place with their cloth mothers, they clung to her until they felt secure enough to explore. Even once they began to explore they would occasionally return to the cloth mother for comfort. Monkeys placed in a strange place without their cloth mothers acted very differently. They would freeze in fear and cry, crouch down, or suck their thumbs. Some of the monkeys would even run from object to object searching for the cloth mother as they cried and screamed. But what is most surprising about this experiment is that monkeys placed in this situation with their wire mothers exhbited the same behaviors that the monkeys with no mother accompaning them did.

Once the monkeys reached an age where they could eat solid foods they were separated from their cloth mothers for 30 days. When they were reunited with their mothers in the same strange room for three minutes they clung to them and did not venture off to explore like they had in previous situations. Harlow determined from this that the need for contact comfort was stronger than the need to explore.

The study also found that monkeys who were raised with only a wire mother or a cloth mother gained weight at the same rate. However, the monkeys that only had a wire mother had trouble digesting the milk and suffered from diarrhea more frequently. These results suggest that not having contact comfort was psychologically stressful to the monkeys. Both groups showed behavior disorders as they grew up as a result of a lack of social interaction.

These findings contradicted both the then common American pedagogic advice of limiting or avoiding bodily contact in an attempt to avoid spoiling especially male children and the insistence of the then dominant behaviorist school of psychology that emotions were negligible. Feeding was thought to be the most important factor in the formation of a mother-child bond. However, Harlow stated that nursing strengthened the mother-child bond because of the intimate body contact that it provided. Harlow himself described his experiments as a study of love. He also believed that contact comfort could be provided by either mother or father. This idea is widely accepted now but was revolutionary in the time that Harlow lived.

While Harlow's result were very dramatic and profound, many people questioned whether his research was applicable to human beings. Many studies that followed have offered evidence supporting the idea that the attachment of human children to their caregivers goes far beyond a desire for biological needs to be fulfilled.

Harlow's research, while controversial, has provided insight into the behaviors of abused children, has improved methods of giving care to institutionalized children, and has allowed fathers and adoptive parents to feel confident in providing parental care.

A rhesus monkey infant in one of Harlow's isolation chambers. The photograph was taken when the chamber door was raised for the first time after six months of total isolation.[1]

From around 1960 onwards, Harlow and his students began publishing their observations on the effects of partial and total social isolation. Partial isolation involved raising monkeys in bare wire cages that allowed them to see, smell, and hear other monkeys, but provided no opportunity for physical contact. Total social isolation involved rearing monkeys in isolation chambers that precluded any and all contact with other monkeys.

Harlow et al reported that partial isolation resulted in various abnormalities such as blank staring, stereotyped repetitive circling in their cages, and self-mutilation. These monkeys were then observed in various settings. Some of the monkeys remained in solitary confinement for 15 years.[2]

In the total isolation experiments baby monkeys would be left alone for three, six, 12, or 24[3][4] months of "total social deprivation." The experiments produced monkeys that were severely psychologically disturbed. Harlow wrote:

No monkey has died during isolation. When initially removed from total social isolation, however, they usually go into a state of emotional shock, characterized by ... autistic self-clutching and rocking. One of six monkeys isolated for 3 months refused to eat after release and died 5 days later. The autopsy report attributed death to emotional anorexia.
... The effects of 6 months of total social isolation were so devastating and debilitating that we had assumed initially that 12 months of isolation would not produce any additional decrement. This assumption proved to be false; 12 months of isolation almost obliterated the animals socially ...[5]

Harlow tried to reintegrate the monkeys who had been isolated for six months by placing them with monkeys who had been reared normally.[6][7] The rehabilitation attempts met with limited success. Harlow wrote that total social isolation for the first six months of life produced "severe deficits in virtually every aspect of social behavior."[8] Isolates exposed to monkeys the same age who were reared normally "achieved only limited recovery of simple social responses."[8] Some monkey mothers reared in isolation exhibited "acceptable maternal behavior when forced to accept infant contact over a period of months, but showed no further recovery."[8] Isolates given to surrogate mothers developed "crude interactive patterns among themselves."[8] Opposed to this, when six-month isolates were exposed to younger, three-month-old monkeys, they achieved "essentially complete social recovery for all situations tested."[9] The findings were confirmed by other researchers, who found no difference between peer-therapy recipients and mother-reared infants, but found that artificial surrogates had very little effect.[10]

Harlow was well known for refusing to use euphemisms and instead chose deliberately outrageous terms for the experimental apparatus he devised, including a forced mating device he called a "rape rack," tormenting surrogate mother devices he called "iron maidens," and in about 1971, an isolation chamber he called the "pit of despair" developed by him and a student, Steven Suomi, now director of the National Institute of Child Health and Human Development's Comparative Ethology Laboratory, at the National Institutes of Health.

In the latter of these devices, alternatively called the "well of despair," baby monkeys were left alone in darkness for up to one year from birth, or repetitively separated from their peers and isolated in the chamber. These procedures quickly produced monkeys that were severely psychologically disturbed and declared to be valuable models of human depression.[11]

Harlow tried to rehabilitate monkeys that had been subjected to varying degrees of isolation using various forms of therapy. "In our study of psychopathology, we began as sadists trying to produce abnormality. Today we are psychiatrists trying to achieve normality and equanimity." (p.458)[12]